1. Field of the Invention
This invention relates to a system for processing a surround signal. This invention relates to a method of processing a surround signal. This invention relates to an information recording medium which stores a surround signal processing program. This invention relates to a transmission system for a surround signal processing program. This invention relates to a reception system for a surround signal processing program. This invention relates to an apparatus for recording a surround signal. This invention relates to a method of recording a surround signal. This invention relates to a recording apparatus for a surround signal processing program.
2. Description of the Related Art
Systems for recovering multiple-channel audio signals are of several types such as the 3-1 type in High-Vision and the 4-channel matrix type based on Dolby surround. Many motion-picture films have surround tracks which carry surround information resulting from Dolby surround audio processing. In a motion-picture theater, sound information is reproduced from a surround track, and the reproduced sound information is decoded into multiple-channel sound signals. The sound signals are fed to loudspeakers before being converted into corresponding sounds, respectively. The loudspeakers include front loudspeakers and also a rear loudspeaker to provide the surround effect.
There are commercially available video tapes and laser discs which are made on the basis of such motion-picture films by steps including a step of copying sound information. These video tapes and laser discs store sound information which results from surround audio processing such as Dolby surround audio processing.
During the reproduction of information from a conventional package recording medium having a surround track, sound information is reproduced from the surround track, and is decoded into 4-channel signals of Dolby surround. It is known to convert such 4-channel signals into only 2-channel signals for a typical audio system without any rear loudspeaker. The 2-channel signals are fed to two front loudspeakers, respectively. The conversion of the 4-channel signals into the 2-channel signals is designed to provide a virtual rear loudspeaker for the surround effect.
Japanese published unexamined patent applications 6-233394 and 8-51698 disclose such surround signal processors having stages for converting 4-channel signals into 2-channel signals. Generally, the surround signal processors in Japanese applications 6-233394 and 8-51698 are required to process input signals at high rates since they implement neither signal compression processes nor signal thinning processes.